Apparatus and method for communicating signaling information

ABSTRACT

A User Equipment, UE, of a cellular communication system transmits scheduling assistance data to a base station comprising a base station scheduler which schedules packet data. The scheduling assistance data relates to packet data communication of the UE. The scheduling assistance data is generated by a scheduling assistance data generator coupled to a packet data transmit buffer associated with the packet data transmission. A first transport channel controller allocates other data to a first transport channel and a retransmission controller operates a retransmission scheme for this transport channel. A second transport channel controller allocates the scheduling assistance data to a signaling transport channel and a transport channel multiplexer combines the two transport channels as multiplexed channels on a single physical resource. The transmission reliabilities for the retransmission and non-retransmission transport channels may be individually optimized.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.K. application GB 0508801.8 filedMay 3, 2005. The contents of this document are incorporated herein byreference.

TECHNICAL FIELD

The invention relates to signaling of scheduling assistance data in acellular communication system and in particular, but not exclusively, tosignaling in a 3^(rd) Generation Partnership Project (3GPP) cellularcommunication system.

BACKGROUND ART

Currently, 3rd generation cellular communication systems are beingrolled out to further enhance the communication services provided tomobile users. The most widely adopted 3rd generation communicationsystems are based on Code Division Multiple Access (CDMA) and FrequencyDivision Duplex (FDD) or Time Division Duplex (TDD). In CDMA systems,user separation is obtained by allocating different spreading and/orscrambling codes to different users on the same carrier frequency and inthe same time intervals. In TDD user separation is achieved by assigningdifferent time slots to different users in a similar way to TDMA.However, in contrast to TDMA, TDD provides for the same carrierfrequency to be used for both uplink and downlink transmissions. Anexample of a communication system using this principle is the UniversalMobile Telecommunication System (UMTS). Further description of CDMA andspecifically of the Wideband CDMA (WCDMA) mode of UMTS can be found in‘WCDMA for UMTS’, Harri Holma (editor), Antti Toskala (Editor), Wiley &Sons, 2001, ISBN 0471486876.

In order to provide enhanced communication services, the 3rd generationcellular communication systems are designed for a variety of differentservices including packet based data communication. Likewise, existing2^(nd) generation cellular communication systems, such as the GlobalSystem for Mobile communications (GSM) have been enhanced to support anincreasing number of different services. One such enhancement is theGeneral Packet Radio System (GPRS), which is a system developed forenabling packet data based communication in a GSM communication system.Packet data communication is particularly suited for data services whichhave a dynamically varying communication requirement such as for exampleInternet access services.

For cellular mobile communication systems in which the traffic andservices have a non-constant data rate, it is efficient to dynamicallyshare radio resources amongst users in accordance with their needs at aparticular instant. This is in contrast to services with constant datarates, where radio resources appropriate for the service data rate canbe assigned on a long-term basis such as for the duration of the call.

In the current UMTS TDD standards, uplink shared radio resources may bedynamically assigned (scheduled) by a scheduler in a Radio NetworkController (RNC). However, in order to operate efficiently, thescheduler needs to have knowledge of the volume of uplink data which iswaiting for uplink transmission at the individual mobile users. Thisallows the scheduler to assign resources to users who need them most andin particular prevents that resource is wasted by being assigned tomobile stations that do not have any data to send.

A further aspect of efficient scheduling is the consideration of userradio channel conditions. A user for whom the radio path gain to anothercell is similar to the radio path gain to the current serving cell maycause significant interference in the other cell. It can be shown thatsystem efficiency may be significantly improved if the scheduler takesinto account the relative path gains from the user to each cell in theparticular locale of the network. In such schemes, the power oftransmissions by users for whom the path gain to one or more non-servingcells is of similar magnitude to the path gain to the current servingcell is restricted such that the inter-cell interference caused iscontrolled and managed. Conversely, the transmit power of transmissionsby users for whom the path gain to the serving cell is far greater thanthat to other cells is relatively less restricted since the inter-cellinterference caused by such users per unit of transmission power isless.

In practical systems, both the radio conditions and the pending datavolume status may change very rapidly. In order to optimize systemefficiency as these changes occur, it is important that the scheduler inthe network is informed of the very latest conditions such that timelyadjustment of the scheduler operation may be effected.

For example, during a typical active session, there will be periodicspurts of uplink data to send (for example when sending an email,sending completed Internet forms, or when sending TCP acknowledgementsfor a corresponding downlink transfer, such as a web page). These shortdata spurts are known as packet calls, and their duration may span fromtypically a few milliseconds to a few seconds. During a packet call,uplink resources are being frequently allocated and it is efficient forthe buffer volume and radio channel information to be piggybacked onthese uplink transmissions to continually update the scheduler as to thedata sending needs of the user. However, once the packet call hascompleted (all data to send has been sent and the transmission buffer istemporarily empty), allocation of uplink resources is suspended. In thissituation, means for informing the scheduler of the arrival of new data(at the start of a new packet call) must be found. It is important tominimize any delay in this signaling since this contributes directly tothe user-perceived transmission speed.

Release 99 of the Technical Specifications for 3GPP UMTS TDD, define alayer 3 message termed the PUSCH (Physical Uplink Shared Channel)Capacity Request (PCR) message. The logical channel carrying PCR (termedthe Shared Channel Control Channel—SHCCH) may be routed to differenttransport channels depending on the presence of available resources. Forexample, the PCR message may be sent on the Random Access CHannel (RACH)which is terminated within the RNC. As another example, if the resourcesare available, the PCR may also in some cases be sent on the UplinkShared CHannel (USCH).

However, although this approach is suitable for many applications it isnot optimal for many other applications. For example, the definedsignaling is aimed at providing scheduling information to RNC basedschedulers and is designed for this application, and is in particulardesigned with a dynamic performance and delay suited for this purpose.Specifically, the signaling is relatively slow and the allocationresponse by the RNC scheduler is not particularly fast due to the delaysassociated with communication between the base station and the RNC (overthe lub interface) and the protocol stack delay in receiving the PCR andtransmitting the allocation grant message via peer-to-peer layer 3signaling.

Recently, significant effort has been invested in improving specificallyuplink performance for 3GPP systems. One way to do this is to move thescheduling entity out of the RNC and into the base stations such thattransmission and retransmission latencies may be reduced. As a result, amuch faster and more efficient scheduling can be achieved. This in turnincreases perceived end-user throughput. In such an implementation, ascheduler located in the base station (rather than in the RNC) assumescontrol over the granting of uplink resources. Fast scheduling responseto user's traffic needs and channel conditions is desirable in improvingthe efficiency of the scheduling and the transmission delays for theindividual mobile stations.

However, as the efficiency of the scheduling activity relies onsufficient information being available, the requirements for thesignaling functionality become increasingly severe. Specifically, theexisting approach wherein signaling is transmitted to the RNC by layer 3signaling, is inefficient and introduces delays which limit thescheduling performance of a base station based scheduler. In particular,using techniques identical to the prior art (such as the use of PCRmessages) are not attractive due to the fact that the transport channelsused are terminated in the RNC—the signaling information thus ends up ina different network entity than that in which the scheduler resides andan additional delay is introduced in communicating this to the basestation scheduler.

For example, in a 3GPP TDD system, timely updates on radio channelconditions are especially important due to the fact that the uplink anddownlink radio channels are reciprocal. As such, if the user is able toinform the network scheduler of the very latest channel conditions (ase.g. measured on the downlink), and the scheduler is able to respondwith minimal delay, then the scheduler may exploit the reciprocity andassume that the radio channel conditions will be relatively unchanged bythe time an uplink transmission is scheduled and transmitted. Thechannel conditions that may be reported by a mobile station may includethe channel conditions for the cell of the scheduler but may alsoinclude channel conditions relating to other cells thereby allowing afast and efficient scheduling taking into account the instantaneousconditions for other cells and the resulting intercell interferencecaused.

As another example, in 3GPP FDD systems, mobile station buffer volumestatus is signalled within the uplink transmissions themselves. The datais contained within the same Protocol Data Unit (PDU) as the otheruplink payload data—specifically in the MAC-e PDU header. However, thismeans that the signaling information is dependent on the performance andcharacteristics of the uplink data transmissions themselves.

In particular, the uplink data transmissions are designed for efficientthroughput and characteristics suited for the data being transmitted.

The delay experienced by packet data transmissions may comprise acomponent due to the queuing of users and a component due to thetransmission itself. In a loaded system, it is common that the queuingdelay is larger than the transmission delay. The capacity of the systemmay be improved by using the radio resources more efficiently. Highercapacity can mean that users are served more quickly, and so the queuingdelay may be reduced. However, some techniques, involving one or moreair interface retransmissions, afford an increase in efficiency (andhence capacity) but at the expense of transmission delay. Thus a balancemust be struck between queuing delay and transmission delay in order tofind a system operating point which optimizes the system performance asperceived by the end-user. Typically many packet data services arerelatively delay tolerant and the communication characteristics aretherefore frequently aimed at an efficient transmission of data using aminimum of the air interface resource. Consequently, link efficiency isprioritized higher than transmission delay in order to reduce queuingdelay for the data traffic. However, the consequential increasedtransmission delay may render the approach unsuitable for carryingcontrol signaling information to a base station scheduler and may resultin an inefficient scheduling by this scheduler.

Specifically, in order to achieve an efficient communication of databits across the air interface, retransmission of data packets which arenot correctly received has been specified for most 3GPP packet dataservices. In such systems, data retransmissions are commonplace andhybrid and fast retransmission schemes are typically used because theoptimum link efficiency (in terms of the energy required per error-freetransmitted bit following retransmissions) is achieved when theprobability of error for first-time transmissions is relatively high(e.g. 10% to 50%). However, the air interface transmission delayassociated with a retransmission is very high as it includes the delayof the acknowledgement feedback process (e.g. the delay of waiting for apossible acknowledgement before deciding to retransmit) and of thescheduling of a retransmission data packet.

Thus, current signaling techniques are suboptimal for many base stationbased schedulers. For example, uplink signaling techniques adopted for3GPP FDD uplink suffer from latencies which, if applied to a TDD uplinksystem, may significantly degrade the performance of that TDD systemwith respect to the level of performance that is achievable.

Hence, an improved signaling in a cellular communication system would beadvantageous and in particular a system allowing increased flexibility,reduced signaling delay, improved scheduling, suitability for basestation based scheduling and/or improved performance would beadvantageous.

SUMMARY OF THE INVENTION

Accordingly, the Invention seeks to preferably mitigate, alleviate oreliminate one or more of the abovementioned disadvantages singly or inany combination.

According to a first aspect of the invention, there is provided, anapparatus for transmitting signaling information in a cellularcommunication system; the apparatus comprising: means for generatingscheduling assistance data for a base station based scheduler, thescheduling assistance data relating to packet data communication of aUser Equipment; means for allocating the scheduling assistance data to afirst transport channel; means for allocating other data to a secondtransport channel; means for transmitting the first and second transportchannel as multiplexed transport channels on a first physical resource;wherein the second transport channel employs a retransmission scheme andthe first transport channel does not employ a retransmission scheme.

The invention may allow improved scheduling by a base station basedscheduler resulting in an improved performance of the cellularcommunication system as a whole. The invention may allow improvedperformance as perceived by the end-users. The invention may e.g.provide increased capacity, reduced delays and/or increased effectivethroughput. The invention may allow a flexible signaling and may allowthe scheduling assistance data to be provided with short delays. Theinvention may in particular provide for signaling of schedulingassistance data which is particularly suitable for a scheduler based ina base station.

The invention may allow a single physical resource to provide animproved signaling of scheduling assistance data while allowing otherdata to be communicated with high link efficiency followingretransmissions. In particular, delay may be reduced for signaling ofscheduling assistance data while ensuring sufficient high reliabilityand link efficiency of other data. Individual trade offs between delayand link efficiency may be made for the transmission of schedulingassistance data and other data. The invention may be compatible withsome existing communication systems, such as 3GPP cellular communicationsystems.

The scheduling assistance data may e.g. comprise an indication of anamount of data pending transmission at the UE and/or an indication ofair interface channel conditions for the UE.

A physical resource may for example be a group of one or more physicalchannels of the cellular communication system. The packet datacommunication of the UE may e.g. be a shared uplink or downlink packetdata service and/or channel.

The apparatus for receiving uplink signaling information may be the UserEquipment.

According to an optional feature of the invention, the means fortransmitting is arranged to transmit the first and second transportchannels with different transmission reliabilities.

This may allow improved communication and may specifically allow lowdelay transmission of the scheduling assistance data while achievinghigh link efficiency for the second transport channel. The transmissionreliabilities may be optimized for the individual characteristics andpreferences for the transmission of the scheduling assistance data andfor a data communication using retransmission. Thus, data packetstransmitted on the first physical resource may comprise data of thefirst transport channel having one transmission reliability and data ofthe second transport channel having a different transmissionreliability.

The means for transmitting may thus be arranged to transmit a datapacket with different transmission reliabilities for data of the firsttransport channel and data of the second transport channel.Retransmissions may further affect the resulting received error rate andmay in particular substantially avoid errors on the second transportchannel.

According to an optional feature of the invention, the means fortransmitting is arranged to transmit the first transmit channel with alower bit error rate than for the second transport channel.

The data of the second transport channel may for example be transmittedwith a data packet error rate more than ten times higher than for thefirst transport channel. This may allow efficient and low delaycommunication of the scheduling assistance data while providing highlink efficiency and an efficient retransmission operation for the secondtransport channel. The bit error rate may relate to the bit error ratefollowing forward error correcting decoding, i.e. the information bitrate following decoding but prior to retransmissions. The reliabilitiesof the first and second transport channels may be represented by blockor packet error rate metrics following forward error correctingdecoding.

The means for transmitting may thus be arranged to transmit a datapacket with different bit error rates for data of the first transportchannel and data of the second transport channel. Retransmissions mayfurther affect the resulting received error rate and may in particularsubstantially avoid errors on the second transport channel.

According to an optional feature of the invention, the means fortransmitting is arranged to transmit the first transport channel inaccordance with a first transmission scheme and to transmit the secondtransport channel in accordance with a different second transmissionscheme.

This may allow improved performance and may in particular allowefficient communication of other data while ensuring fast transmissionfor the scheduling assistance data. In particular it may allow apractical and low complexity implementation allowing individualoptimization and trade offs for the communication of schedulingassistance data and other data using a common first physical resource.

According to an optional feature of the invention, the firsttransmission scheme and second transmission scheme comprise differenterror correcting encoding.

This may allow improved performance and may in particular allowefficient communication of other data while ensuring fast transmissionfor the scheduling assistance data. In particular it may allow apractical and low complexity implementation allowing individualoptimization and trade offs for the communication of schedulingassistance data and other data using a common first physical resource.In particular the effective bit error rates/packet error rates may beeffectively controlled to provide the desired performance.

According to an optional feature of the invention, the means fortransmitting is arranged to perform rate matching of the first transportchannel and the second transport channel.

The rate matching may be performed in order to adjust the errorcorrecting capability of the first and second transport channels. Thismay allow improved performance and a practical implementation and may inparticular provide improved sharing of the physical resource between atleast the first and second transport channels.

According to an optional feature of the invention, the means fortransmitting is arranged to apply different rate matchingcharacteristics to the first transport channel and the second transportchannel.

The different rate matching characteristics may be selected to result indifferent transmission reliabilities for the data of the first andsecond transport channel prior to retransmissions. This may allowimproved performance and may in particular allow efficient communicationof other data while ensuring fast transmission for the schedulingassistance data. In particular, it may allow a practical and lowcomplexity implementation allowing individual optimization for thecommunication of scheduling assistance data and other data using acommon first physical resource. In particular, the effective bit errorrates/packet error rates may be effectively controlled to provide thedesired performance. For example, the rate matching may use differentcode puncturing or channel symbol repetition characteristics for thefirst and second transport channels.

According to an optional feature of the invention, the first transportchannel is terminated in a base station of the base station basedscheduler.

This may allow improved scheduling and may in particular allow a fasterand lower complexity signaling of scheduling assistance data. Inparticular, in existing cellular communication systems, a new transportchannel may be introduced which is particularly suitable for schedulingperformed at a base station and/or for shared communication ofscheduling assistance data and other data.

According to an optional feature of the invention, the first transportchannel has a different termination point than the second transportchannel.

The first transport channel may be terminated in a different networkentity than the second transport channel. For example, the firsttransport channel may be terminated at the base station while the secondtransport channel is terminated at an RNC. The feature may allow aparticularly suitable signaling system and may allow faster signaling ofscheduling assistance data and thus improved scheduling while allowingefficient sharing of physical resources.

According to an optional feature of the invention, the retransmissionscheme is a Radio Network Controller controlled retransmission scheme.

This may allow improved performance in many communication systems andmay for example allow scheduling assistance data to be effectivelycommunicated to a base station based scheduler while allowing other datato be effectively controlled by a Radio Network Controller.

According to an optional feature of the invention, the retransmissionscheme is a Base Station controlled retransmission scheme.

This may allow increased compatibility and/or improved performance inmany communication systems.

According to an optional feature of the invention, the retransmissionscheme is a Hybrid Automatic Repeat reQuest, ARQ, retransmission scheme.

This may allow increased compatibility with existing communicationsystem and/or improved performance in many communication systems. Inparticular, it may allow a particularly efficient communication of otherdata on the same physical resource as used for communication ofscheduling assistance data. Specifically, a Hybrid ARQ scheme mayprovide particularly high link efficiency if high packet data errorrates can be used. In a Hybrid ARQ schemes previous transmissions of adata packet are in the receiver combined with the retransmissions of thedata packet.

According to an optional feature of the invention, the apparatus furthercomprises means for transmitting the scheduling assistance data using asecond physical resource and selection means for selecting between thefirst physical resource and the second physical resource.

This may improve performance and may allow a communication of thescheduling assistance data which is particularly suitable for thecurrent conditions and the current characteristics of the physicalresources. For example, in a 3GPP system, the apparatus may selectbetween a physical random access channel (e.g. PRACH), a dedicatedphysical channel (e.g. DPCH) and/or an uplink channel scheduled by thebase station based scheduler.

According to an optional feature of the invention, the selection meansis arranged to select between the first physical resource and the secondphysical resource in response to an availability of the first physicalresource and the second physical resource.

This may allow efficient signaling and may for example allow schedulingassistance data to be communicated on currently available resources thusallowing a dynamic system wherein the scheduling assistance data iscommunicated on different resources as and when they are available. Suchan arrangement may in particular allow the signaling delay to besubstantially reduced. For example, in a 3GPP system, the apparatus mayselect between a random access physical channel (e.g. PRACH), adedicated physical channel (e.g. DPCH) and/or an uplink channelscheduled by the base station based scheduler depending on which ofthese channels are currently set up. The availability may for example bea duration since the physical resource was available.

According to an optional feature of the invention, the selection meansis arranged to select between the first physical resource and the secondphysical resource in response to a traffic loading of the first physicalresource and the second physical resource.

This may allow efficient signaling and may for example allow schedulingassistance data to be communicated on physical resources that haveexcess capacity. For example, in a 3GPP system, the apparatus may selectbetween a physical random access channel (e.g. PRACH), a dedicatedphysical channel (e.g. DPCH) and/or an uplink channel scheduled by thebase station based scheduler depending on which of these channels havespare capacity.

In some embodiments, the selection means is arranged to select betweenthe first physical resource and the second physical resource in responseto a latency characteristic associated with the first physical resourceand the second physical resource.

This may allow efficient signaling and may for example allow schedulingassistance data to be communicated on the physical resource that resultsin the lowest delay for the scheduling assistance data. This may provideimproved performance and scheduling due to reduced delay. The latencycharacteristic may e.g. be an estimated, assumed or calculated delay fortransmission of the scheduling assistance data on each physicalresource.

According to an optional feature of the invention, the first physicalresource is not managed by the base station based scheduler.

This may provide efficient and low delay signaling of schedulingassistance data. The data on the first physical resource is notscheduled by the base station based scheduler. Rather the data on thefirst physical resource may for example be scheduled by a scheduler ofthe RNC supporting the base station of the base station based scheduler.The first physical resource may be a resource which the base stationbased scheduler does not have any controlling relationship with and/orinformation of.

According to an optional feature of the invention, the second physicalresource is a physical resource managed by the base station basedscheduler.

The second physical resource may support data which is scheduled by thebase station based scheduler. The second physical resource mayspecifically support a user data channel for which the base stationbased scheduler schedules the information. For example, in a 3GPPsystem, the apparatus may select between a physical random accesschannel (e.g. PRACH), a dedicated physical channel (e.g. DPCH)controlled by an RNC scheduler and/or a packet data uplink channel whichis scheduled by the base station based scheduler.

According to an optional feature of the invention, the first physicalresource is associated with the first transport channel and the secondphysical resource is associated with a third transport channel and theselection means is arranged to allocate the scheduling assistance databy associating the scheduling assistance data with the first or thirdtransport channel.

This may provide a highly advantageous approach and may in particularallow an efficient selection of the appropriate physical resource whileallowing individual optimisation of transmission characteristics for thescheduling assistance data. The transport channels may be selected inresponse to characteristics associated with the physical resource of thetransport channel. The third transport channel may in some embodimentsbe the same as the second transport channel.

According to an optional feature of the invention, the first physicalresource is a random access channel

The random access channel may provide a particularly suitable channel asit may be used when no other physical channels are available.

According to an optional feature of the invention, the packet datacommunication is an uplink packet data communication. The invention mayprovide particularly advantageous performance for an uplink packet datacommunication service which may specifically be an uplink packet datacommunication service.

According to an optional feature of the invention, the cellularcommunication system is a 3^(rd) Generation Partnership Project, 3GPP,system.

The 3GPP system may specifically be a UMTS cellular communicationsystem. The invention may allow improved performance in a 3GPP cellularcommunication system.

According to an optional feature of the invention, the cellularcommunication system is a Time Division Duplex system.

The invention may allow improved performance in a TDD cellularcommunication system and may in particular allow improved scheduling byexploiting the improved signaling of channel condition informationapplicable to both uplink and downlink channels.

According to a second aspect of the invention, there is provided anapparatus for receiving signaling information in a cellularcommunication system; the apparatus comprising: means for receiving afirst physical resource comprising a first transport channel and asecond transport channel as multiplexed transport channels; means forextracting scheduling assistance data for a base station based schedulerfrom the first transport channel, the scheduling assistance datarelating to packet data communication of a User Equipment; means forextracting other data from the second transport channel; and wherein thesecond transport channel employs a retransmission scheme and the firsttransport channel does not employ a retransmission scheme.

It will be appreciated that the optional features, comments and/oradvantages described above with reference to the apparatus fortransmitting uplink signaling information apply equally well to theapparatus for receiving uplink signaling information and that theoptional features may be included in the apparatus for receiving uplinksignaling information individually or in any combination.

The apparatus for receiving uplink signaling information may be a basestation.

According to a third aspect of the invention, there is provided a methodof transmitting signaling information in a cellular communicationsystem; the method comprising: generating scheduling assistance data fora base station based scheduler, the scheduling assistance data relatingto packet data communication of a User Equipment; allocating thescheduling assistance data to a first transport channel; allocatingother data to a second transport channel; transmitting the firsttransport channel and second transport channel as multiplexed transportchannels on a first physical resource; and wherein the second transportchannel employs a retransmission scheme and the first transport channeldoes not employ a retransmission scheme.

It will be appreciated that the optional features comments and/oradvantages described above with reference to the apparatus fortransmitting uplink signaling information apply equally well to themethod for transmitting uplink signaling information and that theoptional features may be included in the method for transmitting uplinksignaling information individually or in any combination.

For example, in accordance with an optional feature of the invention,the first transport channel and the second transport channel aretransmitted with different transmission reliabilities.

As another example, in accordance with an optional feature of theinvention, the first transport channel is transmitted in accordance witha first transmission scheme and the second transport channel istransmitted in accordance with a different second transmission scheme.

As another example, in accordance with an optional feature of theinvention, the first transport channel is terminated in a base stationof the base station based scheduler.

According to a fourth aspect of the invention, there is provided amethod of receiving signaling information in a cellular communicationsystem; the method comprising: receiving a first physical resourcecomprising a first transport channel and a second transport channel asmultiplexed transport channels; extracting scheduling assistance datafor a base station based scheduler from the first transport channel, thescheduling assistance data relating to packet data communication of aUser Equipment; extracting other data from the second transport channel;and wherein the second transport channel employs a retransmission schemeand the first transport channel does not employ a retransmission scheme.

These and other aspects, features and advantages of the invention willbe apparent from and elucidated with reference to the embodiment(s)described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be described, by way of example only,with reference to the drawings, in which

FIG. 1 illustrates an example of a cellular communication system 100 inwhich embodiments of the invention may be employed;

FIG. 2 illustrates a UE, an RNC and a base station in accordance withsome embodiments of the invention;

FIG. 3.a illustrates an example of the switching of a single transportchannel between uplink physical resource types;

FIG. 3.b illustrates an example of the switching of the signalinginformation stream into two or more transport channels each of which hasa fixed association with a physical resource type; and

FIG. 4 illustrates and example of a signaling system in accordance withsome embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description focuses on embodiments of the inventionapplicable to a UMTS (Universal Mobile Telecommunication System)cellular communication system and in particular to a UMTS TerrestrialRadio Access Network (UTRAN) operating in a Time Division Duplex (TDD)mode. However, it will be appreciated that the invention is not limitedto this application but may be applied to many other cellularcommunication systems including for example a GSM (Global System forMobile communication system) cellular communication system.

FIG. 1 illustrates an example of a cellular communication system 100 inwhich embodiments of the invention may be employed.

In a cellular communication system, a geographical region is dividedinto a number of cells each of which is served by a base station. Thebase stations are interconnected by a fixed network which cancommunicate data between the base stations. A mobile station is servedvia a radio communication link by the base station of the cell withinwhich the mobile station is situated.

As a mobile station moves, it may move from the coverage of one basestation to the coverage of another, i.e. from one cell to another. Asthe mobile station moves towards a base station, it enters a region ofoverlapping coverage of two base stations and within this overlap regionit changes to be supported by the new base station. As the mobilestation moves further into the new cell, it continues to be supported bythe new base station. This is known as a handover or handoff of a mobilestation between cells.

A typical cellular communication system extends coverage over typicallyan entire country and comprises hundreds or even thousands of cellssupporting thousands or even millions of mobile stations. Communicationfrom a mobile station to a base station is known as uplink, andcommunication from a base station to a mobile station is known asdownlink.

In the example of FIG. 1, a first User Equipment (UE) 101 and a secondUE 103 are in a first cell supported by a base station 105. A UE may befor example a remote unit, a mobile station, a communication terminal, apersonal digital assistant, a laptop computer, an embedded communicationprocessor or any communication element communicating over the airinterface of the cellular communication system.

The base station 105 is coupled to an RNC 107. An RNC performs many ofthe control functions related to the air interface including radioresource management and routing of data to and from appropriate basestations.

The RNC 107 is coupled to a core network 109. A core networkinterconnects RNCs and is operable to route data between any two RNCs,thereby enabling a remote unit in a cell to communicate with a remoteunit in any other cell. In addition, a core network comprises gatewayfunctions for interconnecting to external networks such as the PublicSwitched Telephone Network (PSTN), thereby allowing mobile stations tocommunicate with landline telephones and other communication terminalsconnected by a landline. Furthermore, the core network comprises much ofthe functionality required for managing a conventional cellularcommunication network including functionality for routing data,admission control, resource allocation, subscriber billing, mobilestation authentication etc.

It will be appreciated that for clarity and brevity only the specificelements of the cellular communication system required for thedescription of some embodiments of the invention are shown, and that thecellular communication may comprise many other elements including otherbase stations and RNCs as well as other network entities such as SGSNs,GGSNs, HLRs, VLRs etc.

Conventionally, the scheduling of data over the air interface isperformed by the RNC. However, recently packet data services have beenproposed which seek to exploit the fluctuating channel conditions whenscheduling data over a shared channel. Specifically, a High SpeedDownlink Packet Access (HSDPA) service is currently being standardizedby 3GPP. HSDPA allows scheduling to be performed taken the conditionsfor the individual UEs into account. Thus, data may be scheduled for UEswhen channel propagations allow for this to be communicated with lowresource usage. However, in order to enable this scheduling to besufficiently fast to follow the dynamic variations, HSDPA requires thatthe scheduling is performed at the base station rather than by the RNC.Locating a scheduling function in the base station eliminates therequirement for communication over the base station to RNC interface(the lub interface) thereby reducing the significant delays associatedtherewith.

In order for the scheduling to be efficient, the base station schedulerneeds current information of the channel conditions. Accordingly, in aTDD HSDPA system, the mobile station provides information bytransmitting this information to the base station using a channel whichis controlled by the downlink scheduler. Uplink resources (denotedHS-SICH) are implicitly assigned when the UE receives an allocation fordownlink HSDPA data, such that a positive or negative acknowledgement ofthat downlink data may be returned to the base station based downlinkscheduler. In addition to transmitting the acknowledgement informationon the implicitly-assigned uplink physical resources, the UE alsoincludes current information of the channel conditions. Thus,information is transmitted to the scheduler on the HS-SICH which is setup and controlled by the scheduler controlling the HSDPA communication.Furthermore, dedicated resources are used for the uplink signaling andthe HS-SICH may be permanently set up to provide the requiredinformation.

It has recently been proposed to introduce an uplink packet data servicesimilar to HSDPA. In particular, such a service would utilise a basestation based scheduler to schedule user data on an uplink packetchannel. However, in order for such a system to operate efficiently, itis necessary that the scheduler is provided with information from the UEwith a minimum of delay. It has been proposed to provide thisinformation by including the information with the uplink user data.Specifically, it has been proposed to piggyback the data on the useddata packets by including such data in the MAC-e header of the uplinkuser data PDUs (Packet Data Units).

However, a solution where the signaling data is transmitted in user dataPDUs is suboptimal in many situations. In particular, it leads to aninflexible system and restricts the scheduling efficiency. Specifically,in order to achieve an efficient communication of the user data, it hasbeen proposed to use a retransmission scheme for the PDUs. Inparticular, it has been proposed to use an ARQ scheme wherein previoustransmissions of PDUs are combined with the retransmissions in thereceiver. However, in order for such a scheme to operate efficiently,the PDU error rate is selected to be relatively high, resulting in a lowresource usage of each PDU but a significant number of retransmissions.Thus, the signaling data for the base station scheduler will inherentlyhave a high error rate and will typically require retransmissions beforebeing correctly received. However, this introduces a very substantialdelay which significantly reduces the achievable performance of thescheduler. In particular for a TDD system, an increased delay maysignificantly affect the performance which can be achieved.

In the following, some embodiments are described wherein an efficientsharing of a physical resource between scheduling assistance data andother data is achieved while ensuring that the delay of the schedulingassistance data is reduced thus resulting in improved schedulingperformance, improved end user perceived quality of service and improvedperformance of the cellular communication system as a whole.

FIG. 2 illustrates the UE 101, the RNC 107 and the base station 105 ofthe example of FIG. 1 in more detail. In the example, the RNC 107comprises an RNC scheduler 201 which is responsible for schedulingconventional 3GPP physical channels such as for example a DedicatedPhysical CHannel (DPCH) as will be known to the person skilled in theart. Thus, the RNC scheduler 201 schedules data for communication overthe air interface as defined in Release 99 of the 3GPP technicalspecifications.

In the example of FIG. 2, the base station 105 comprises an RNCinterface 203 which is responsible for communicating with the RNC 107over the lub interface. The RNC interface 203 is coupled to a basestation controller 205 which controls the operation of the base station105. The base station controller 205 is coupled to a transceiver 207which is operable to communicate with the UE 101 over the air interface.The base station controller 205 performs all the functionality requiredfor transmitting data received from the RNC 107 to the UE 101 as well asfor receiving and forwarding data received from the UE 101 to the RNC107.

The base station 105 furthermore comprises a base station scheduler 209which is coupled to the base station controller 205. The base stationscheduler 209 is responsible for scheduling data for an uplink packetdata service which may be an uplink shared packet data service.Specifically, the base station scheduler 209 schedules user data on ashared transport channel of a shared physical resource and generatesresource allocation information for the shared physical resource. Theallocation information is fed to the base station scheduler 209 andtransmitted to the UEs 101, 103 over the air interface.

As the base station scheduler 209 is located in the base station 105, itcan schedule data without the additional delay required forcommunication of allocation information over the lub interface (asrequired for the RNC scheduler 201).

The base station scheduler 209 schedules data for the uplink transportchannel based on different information. In particular, the base stationscheduler 209 may schedule data in response to the individual airinterface channel propagation characteristics and the current transmitbuffer requirements of the UEs. Accordingly, this information ispreferably obtained from scheduling assistance data which is transmittedto the base station 105 from the UEs 101, 103. In order to have anefficient scheduling, the scheduling assistance data is preferablyreceived with low delay and frequent intervals. Accordingly, it isdesirable that the scheduling assistance data is provided to the basestation scheduler 209 without it first being transmitted to and receivedfrom the RNC 107 over the lub interface.

In the example of FIG. 2, the UE 101 comprises a transceiver 211 whichis operable to communicate with the base station 105 over the airinterface in accordance with the 3GPP Technical Specifications. It willbe appreciated the UE 101 furthermore comprises the required or desiredfunctionality for a UE of a 3GPP cellular communication system.

The UE 101 comprises a channel controller 213 which is operable toallocate data to individual physical resources in accordance with the3GPP Technical Specifications. In the specific example of FIG. 2, the UE101 is involved in a user data communication and comprises a user datasource 215 which generates user data to be transmitted to the RNC 107.The user data source 215 is coupled to a first transport channelcontroller 217 which allocates the user data to an appropriate transportchannel (henceforth referred to as the user data transport channel) suchas the uplink Dedicated Channel (DCH) or the Uplink Shared Channel(USCH).

The first transport channel controller 217 is further coupled to aretransmission controller 219. The retransmission controller 219 iscoupled to the transceiver and is arranged to operate a retransmissionscheme for the transport channel used for the user data (i.e. the DCH).The retransmission scheme is particularly an ARQ retransmission schemecontrolled by the RNC 107 in accordance with the 3GPP TechnicalSpecifications.

If a data packet comprising user data is acknowledged by the RNC 107,the transceiver 211 feeds the acknowledgement to the retransmissioncontroller 219. The retransmission controller 219 thus monitors thereceived acknowledgements and detects if a data packet has not beenacknowledged. If this occurs, the retransmission controller 219 informsthe first transport channel controller 217 which proceeds to includethis data in the DCH transport channel for the next (or a subsequent)PDU to be transmitted to the base station 105. Thus, the first transportchannel controller 217 ensures that all user data is received by thebase station even if packet errors occur.

In the example of FIG. 2, the UE 101 is furthermore involved in a packetdata communication which is scheduled by the base station scheduler 209.For example, the UE 101 may be involved in an Internet accessapplication supported by an uplink packet data service. In the example,the UE 101 comprises a packet data transmit buffer 221 which stores thepacket data until it is scheduled for transmission over the uplinkchannel which specifically may be an uplink shared channel. However, incontrast to the communication of the user data from the user datasource, the scheduling for this packet data communication is performedby the base station scheduler 209 rather than by the RNC scheduler 201.

The packet data transmit buffer 221 is coupled to the channel controller213 which is arranged to transmit the packet data to the base station105 using an appropriate physical resource and transport channelcontrolled by the base station scheduler 209. Specifically, the channelcontroller 213 may transmit the packet data on an Enhanced DedicatedCHannel (E-DCH).

The packet data transmit buffer 221 is coupled to a schedulingassistance data generator 223 which generates scheduling assistance datafor transmission to the base station 105. In particular, the schedulingassistance data relates to information that is available at the UE 101and which may be used by the base station scheduler 209 when schedulingdata.

In the UE 101 of FIG. 2, the scheduling assistance data generator 223 iscoupled to the packet data transmit buffer 221 and obtains dynamicinformation of the current buffer loading from this. Thus, thescheduling assistance data generator 223 determines how much data iscurrently stored in the packet data transmit buffer 221 pendingtransmission over the uplink channel.

The scheduling assistance data generator 223 includes an indication ofthis pending transmit data amount in the scheduling assistance data.Furthermore, the scheduling assistance data generator 223 may beprovided with information which is indicative of the current propagationconditions and may include this information in the scheduling assistancedata. The propagation conditions for the physical resource may forexample be determined from signal level measurements on receivedsignals. In the example of a TDD system, this downlink propagation datamay be considered applicable for the uplink propagation data as wellsince both uplink and downlink use the same frequency.

The scheduling assistance data generator 223 is coupled to a secondtransport channel controller 225 which allocates the schedulingassistance data to a second transport channel, henceforth referred to asthe signaling transport channel.

The first transport channel controller 217 and the second transportchannel controller 225 are coupled to a transport channel multiplexer227 which is arranged to multiplex the user data transport channel andthe signaling transport channel. The transport channel multiplexer 227is further coupled to the channel controller 213 which is operable totransmit the first and second transport channels as multiplexedtransport channels on a physical resource.

Thus, in the example, the scheduling assistance data is transmitted onthe same physical resource as the user data by the physical resourcebeing shared by two different transport channels. For example, a givenPDU transmitted over the air interface may comprise data from both theuser data transport channel and the signaling transport channel.Furthermore, an efficient and optimized shared communication is achievedwhere one transport channel employs a retransmission scheme whereas theother transport channel does not. In particular, the user data istransmitted using a retransmission scheme which may provide a highlyefficient and low resource communication but may also have a significantdelay. The scheduling assistance data may be transmitted on a signalingtransport channel which does not employ a retransmissions scheme. Thusthe base station scheduler 209 does not need to await retransmissionsbefore scheduling data.

It will be appreciated that in some embodiments, the packet datatransmit buffer may be transmitted on the first transport channel. Thusin some embodiments, the scheduling assistance data may be transmittedon a transport channel which is multiplexed onto the same resource witha transport channel carrying the data to which the scheduling assistancedata relates, whereas in other embodiments it may be multiplexed with atransport channel carrying other data and possibly being unrelated tothe uplink data communication of the packet data from the packet datatransmit buffer. The first transport channel may e.g. carry user data,control data or other signaling data.

In the example of FIG. 2, the user data transport channel is a DCHchannel for which the retransmission is controlled by the RNC 107. Insuch embodiments, the RNC 107 may transmit an acknowledge message to theUE 101 only when it receives a correctly received PDU from the basestation 105. Thus, if the base station 105 receives a PDU without beingable to successfully decode it, the received symbol samples may bestored. As no acknowledge is sent to the UE 101 this will retransmit thePDU and when the new transmission is received by the base station 105,the data is combined with the stored symbol samples. If this allows thePDU to be recovered, this is sent to the RNC 107 which in returntransmits the acknowledge message to the UE 101. Otherwise, the basestation 105 stores the data and awaits the next retransmission from theUE 101.

In other embodiments, the retransmission may be controlled elsewhere.For example, in some embodiments, when the base station 105 successfullyreceives the PDUs from the UE 101, the base station controller 205generates an acknowledge message which is transmitted to the UE 101 bythe transceiver 207. Thus, in this example, the retransmission iscontrolled by the base station 105. The retransmission scheme may insuch embodiments particularly be a Hybrid ARQ scheme.

In the example of FIG. 2, the channel controller 213 transmits thescheduling assistance data over a physical resource which is not managedby the base station based scheduler. In particular, the channelcontroller 213 selects a physical channel which is controlled by the RNCscheduler 201.

As an example, the channel controller 213 may transmit the schedulingassistance data on a dedicated physical resource used for a circuitswitched voice call. Specifically, the channel controller may piggybackthe scheduling assistance data together with a DPDCH which has been setup and is controlled by the RNC scheduler 201, onto DPCH physicalresources assigned which are again set up and controlled by the RNCscheduler 201. As another example, the channel controller may transmitthe scheduling assistance data on a Random Access CHannel (the PRACHchannel).

When the communication is received at the base station 105, the basestation controller 205 is in the example of FIG. 2 arranged to extractthe scheduling assistance data and to feed it to the base stationscheduler 209. For example, the base station controller 205 may monitorthe DPDCH and/or the PRACH and when it detects that schedulingassistance data is being received, it may decode this data and send itto the base station scheduler 209.

It will be appreciated that in some embodiments, the RNC scheduler 201may specifically allocate segments of the physical resource for thecommunication of scheduling assistance data and information identifyingthese segments may be communicated both to the base station 105 and theUE 101.

The scheduling assistance data is thus in this example received on aphysical resource which is shared by other services supported byscheduling in the RNC. In some embodiments, the scheduling assistancedata may be received on a physical resource which is supported by adifferent scheduler in the base station 105, such as in the case ofHS-SICH for HSDPA. Specifically, these services may be conventionalrelease 99, release 4 or release5 services. Thus, an efficient andflexible communication of scheduling assistance data is achieved whilemaintaining backwards compatibility and avoiding the requirement of thebase station scheduler 209 needing to allocate resource for schedulingassistance data. Rather, in many situations, unused resource of the RNCscheduled physical resources may be used for communication of schedulingassistance data.

Furthermore, the system of FIG. 2 allows a very fast communication ofscheduling assistance data as the signaling avoids the delay inherent incommunication over the lub interface between the base station 105 andthe RNC 107.

In the example, the base station scheduler 209 may be provided withscheduling assistance data indicative of the air interface channelconditions and the transmit data requirements of UEs 101, 103 atfrequent intervals (due to the efficient resource utilization) and withvery low delays. This allows a much faster scheduling taking intoaccount fast varying characteristics and thus results in a much improvedscheduling. This leads to an improved resource usage and increasedcapacity of the cellular communication system as a whole.

In the example of FIG. 2, the scheduling assistance data is communicatedon a signaling transport channel. A transport channel may be a channelthat carries PDUs to and from the physical layer and the MAC layer. Aphysical channel carries bits over the air interface. A physical channelis specifically a Layer 1 (Physical layer) channel. A logical channelcarries PDUs between the MAC layer and the RLC (Radio Link Control)layer.

Specifically, for 3GPP systems, a transport channel is aninformation-bearing interface between a 3GPP Multiple Access Control(MAC) entity, and a 3GPP physical layer entity. A physical channel is aunit of transmission resource, defined in 3GPP as a specific spreadingcode and period of time occupancy on the air interface; a unit oftransmission resource. A logical channel is an information-bearinginterface at the transmission input to the MAC.

In the system of FIG. 2, the physical resource supports two or moretransport channels which are multiplexed onto the same physicalresource. Specifically, a new transport channel may be defined forcommunication of the scheduling assistance data and this transportchannel may be multiplexed together with one or more DCH(s) onto one ormore physical DPCH channels on which the DCH(s) are carried in a 3GPPsystem.

For a 3GPP system, two or more separate information streams may bemultiplexed onto a common set of physical resources in several ways:

Physical Layer Field Multiplexing

For physical layer field multiplexing, the multiple information streamsare separately encoded (if required) and occupy mutually exclusive (andusually contiguous) portions of the transmission payload.De-multiplexing is achieved by extracting the relevant portions of thetransmission payload for each stream and treating them independentlythereafter.

Transport Channel Multiplexing

For transport channel multiplexing, the multiple information streams areseparately encoded and a coordinated rate matching scheme is applied toeach stream such that the total number of bits after rate matchingexactly fits the transmission payload. Generally, this is similar tophysical layer multiplexing except that the bits corresponding to eachinformation stream are usually non-contiguous in the final transmissionpayload. Additionally, the rate matching scheme is designed in such away that the amount of FEC applied to each stream may be varied in aflexible manner, allowing for various and differing quality requirementsto be met independently for each stream. De-multiplexing is enabled viathe receiver having knowledge of the rate matching scheme algorithmapplied in the transmitter.

Logical Channel Multiplexing

For logical channel multiplexing, the multiple information streams aremultiplexed by the MAC layer prior to forward error correction encodingby the physical layer, with a header being applied to each stream toenable de-multiplexing in the receiver. FEC encoding is applied to thecomposite (multiplexed) stream, and so each stream will experience thesame transmission reliability.

It will be appreciated that although the physical resource, such as theDPCH channel, is controlled by the RNC scheduler, the transport channelused for the scheduling assistance data is preferably terminated at thebase station 105 while the dedicated transport channel, the DCH, isterminated at the RNC 107. Thus, although the transport channel used forthe scheduling assistance data and the transport channel used for otherdata are multiplexed onto the same physical resource, they terminate indifferent entities. This may allow a particularly efficient and flexiblesignaling and may in particular minimize the delay for the schedulingassistance data. Specifically, it may avoid the delay associated withreceiving the scheduling assistance data on a RNC terminated transportchannel and retransmitting this to the base station 105.

The UE 101 of FIG. 2 employs transport channel multiplexing.Multiplexing of the transport channels provides a number of advantagesand options particularly suitable for the described embodiments.

For example, in contrast to physical layer multiplexing, it enables theuplink signaling to be multiplexed with legacy channels (e.g. Release 99defined channels) without having a large impact on the 3GPP TechnicalSpecifications.

Furthermore, existing approaches for transport channel multiplexingwithin 3GPP may be re-used with minimal impact on the TechnicalSpecifications and thus improved backwards compatibility may beachieved.

Furthermore, usage of transport channel multiplexing may be used toindividually optimize performance for the individual transport channels.In some embodiments, different transmission schemes are used for thedifferent transport channels. In particular, different transmissionschemes resulting in different transmission reliabilities may be used.

As a specific example, the forward error correction coding may beselected individually for each transport channel and for example ahigher reliability forward error correction coding may be selected forthe signaling transport channel than for the user data transportchannel.

As a specific example, the first transport channel controller 217 mayapply a first forward error correction coding scheme, such as a ½ rateViterbi encoding scheme whereas the second transport channel controller225 may apply a different encoding scheme or may use a differentencoding rate. For example, the second transport channel controller 225may apply a ⅓ rate Viterbi encoding scheme.

In some such embodiments, the transport channel multiplexer 227 maysimply multiplex the transport channels by combining the data of thefirst transport channel controller 217 and the second transport channelcontroller 225 in the PDUs to be transmitted on the physical resource.

In the specific example, a higher transmission reliability would thus beachieved for the scheduling assistance data than for the user data. Theeffective bit error and thus packet data error rate may be selected tobe substantially lower, say by a factor of ten, for signaling transportchannel than for the user data transport channel.

This may be highly advantageous as a high link efficiency may beobtained for the user data due to the low resource usage per data packetcombined with retransmissions. At the same time, a highly reliabletransmission of scheduling assistance data may be achieved. Thiscommunication may ensure that the scheduling assistance data may bereceived from a first transmission even if the user data cannot bedetermined from the received signal. Thus, an increased reliability andreduced delay for the scheduling assistance data is achieved.

As another example, the first transport channel controller 217 and thesecond transport channel controller 225 may provide differenttransmission reliabilities by using different modulation schemes. Forexample, the first transport channel controller 217 may generate a userdata transport channel using 8-PSK (Phase Shift Keying) symbols whereasthe second transport channel controller 225 may use QPSK (QuaternaryPhase Shift Keying) data symbols.

In some embodiments, the transport channel multiplexer 227 is furtheroperable to perform rate matching for the user data and signalingtransport channels. This may allow the channel data allocated to a PDUby the first transport channel controller 217 and the second transportchannel controller 225 to be adjusted to match the capacity of the PDU.The transport channel multiplexer 227 may specifically in someembodiments apply different rate matching characteristics to the userdata transport channel and the signaling transport channel.

For example, rate matching may include puncturing of the encoded dataoutput of the first transport channel controller 217 and/or the secondtransport channel controller 225. Puncturing of a code comprisesremoving some redundant symbols from the encoded data and may be used toreduce the resulting encoded data rate.

Alternatively or additionally, rate matching may include repeating someof the encoded data from the first transport channel controller 217and/or the second transport channel controller 225. Repetition ofencoded symbols comprises repeating some of the symbols from the encodeddata and may be used to increase the resulting encoded data rate.

Furthermore, increased puncturing may increase the resulting error rateswhereas repetition may reduce the error rates. Thus, by adjusting thepuncturing and repetition characteristics, the transport channelmultiplexer 227 may adjust the reliability of the transmitted data andby using different puncturing and repetition for the two transportchannels different transmission reliabilities are achieved.

The transport channel multiplexer 227 may specifically use puncturingand repetition to both obtain a desired data rate or data volume whileobtaining a desired relative reliability difference between the userdata transport channel and the signaling transport channel.

Thus, in the example, the user data transport channel employs aretransmission scheme where faulty data packets are retransmitted fromthe UE 101 whereas the signaling transport channel does not employ aretransmission scheme but rather transmits the data with a more reliableerror coding. In the example, a single physical resource may comprise afirst transport channel used for transmission of non-delay-sensitivedata. The transmissions may have a high data packet error rate of, say,10-30% resulting in a large number of retransmissions and thus increaseddelay but also in a very efficient resource utilization. At the sametime, the physical resource may support a signaling transport channelused for the transmission of the scheduling assistance data and thistransport channel may have a very low data rate thus ensuring that thepacket data is received reliably and with a low delay resulting inimproved scheduling by the base station scheduler 209.

It will be appreciated that e.g. physical resources controlled by theRNC 107 may be used to support the communication of the schedulingassistance data.

For example, as described, a DPCH or PRACH physical channel may be used.In some embodiments, the UE 101 and base station 105 may additionallycomprise functionality for communicating the scheduling assistance dataon a physical resource which is managed by the base station scheduler209. Thus, in this example, the UE 101 may comprise functionality forcommunicating on a number of different physical resources. In theexample of FIG. 2, a suitable physical resource on which to communicatethe scheduling assistance data may be selected depending on the currentconditions and operating environment and a suitable physical channel maybe selected to provide the best performance for the current conditions.

Thus, in this example the signaling used to assist the enhanced uplinkscheduling process by the base station scheduler 209 is intelligentlyrouted and transmitted on different uplink physical resources accordingto the current preferences and conditions. In particular, a physicalresource may be selected based on the presence or absence of thoseuplink physical resources. The scheduling assistance data mayfurthermore be communicated in a transport channel which is terminatedin the base station 105.

In an alternative approach, the signaling used to assist the enhanceduplink scheduling process by the base station scheduler 209 may berouted and transmitted on different transport channels, and hence,physical resources, under the control of the network, via network-to-UEsignaling means.

The intelligent-routing approach will be illustrated with reference toan example where three specific configurations are considered:

Scenario 1:

The user equipment 101 intends to inform the base station scheduler 209about its current packet data transmit buffer status or radioconditions, yet no enhanced uplink resources have been granted fortransmission and no other uplink radio resources are in existence or areavailable. This situation is common when the UE 101 has previouslyfinished transmission of a packet call, has been idle for a period oftime, and new data arrives in the UE's 101 packet data transmit buffer221. The user must then inform the base station scheduler 209 of itsneed for transmission resources to transmit the new data.

Scenario 2:

The user equipment 101 intends to update the base station scheduler 209with new air interface condition information or buffer information andpacket data uplink resources scheduled by the base station scheduler 209are already available. In this case, the UE 101 may piggyback the uplinksignaling using a part of the resources granted for transmission of theuplink packet data transmission itself.

Scenario 3:

The user equipment 101 intends to update the base station scheduler 209with new channel or buffer information, no packet data uplink resourcesmanaged by the base station scheduler 209 are available, yet other RNCmanaged uplink resources are in existence and are available. In thiscase, the UE 101 may piggyback the signaling using a part of theexisting uplink resources.

Thus, in some embodiments the channel controller 213 of the UE 101 andthe base station controller 205 of the base station 105 comprisefunctionality for selecting between different physical resources.Furthermore, this selection may be performed in response to whether thedifferent physical resources are available.

As a specific example, the channel controller 213 may first evaluate ifan uplink packet data channel controlled by the base station scheduler209 is available. If so, this channel is selected for transmission ofthe scheduling assistance data. Otherwise, the channel controller 213may evaluate if an uplink physical channel controlled by the RNCscheduler 201 is set up (such as a DPCH). If so, the schedulingassistance data is transmitted on this channel. However, if no suchchannel is available, the channel controller 213 may continue totransmit the scheduling assistance data using a random access channel(the PRACH).

In different embodiments, the selection of physical resources may bemade in response to different parameters or characteristics. Forexample, the channel controller 213 and base station controller 205 maytake into account parameters such as:

The presence or absence of uplink physical resource types.

The time since an uplink physical resource type was last present. Forexample, a given physical resource may be selected only if it has beenavailable within a given time interval.

The traffic loading of channels mapped to the uplink resource types. Forexample, a physical resource may be selected if the traffic loading isso low that there is spare available resource.

A consideration of the transmission latency of the uplink signaling. Forexample, each physical resource may have an associated latency due tosignaling delays, encoding etc. and the physical resource having thelowest latency may be selected in preference to other physicalresources.

Alternatively or additionally, the selection of the physical resourcemay be performed in response to a configuration by the fixed network andin particular the RNC. For example, some signaling routes may beexplicitly allowed or disallowed by the fixed network.

The selection of physical resources may for example be made by selectinga transport channel and then selecting a physical resource on which totransmit this transport channel. As another example, the selection ofphysical resources may be made by having different transport channelslinked to different physical channels and then selecting the appropriatetransport channel.

FIG. 3 illustrates the principles between these exemplary switchingembodiments. In particular, FIG. 3 a illustrates an example of theswitching of a single transport channel between uplink physical resourcetypes and FIG. 3.b illustrates an example of the switching of thesignaling information stream into two or more transport channels eachhaving a fixed association with a physical resource type.

In the example of FIG. 3 a, the scheduling assistance data is includedin a new transport channel (TrCH #1). The transport channel is thenswitched either to a first or second transport channel multiplexerdepending on the desired physical resource type. The selected transportchannel multiplexer multiplexes the transport channels with othertransport channels to be communicated on the physical resource.

In the example of FIG. 3 b, the scheduling assistance data is eitherincluded in a first transport channel (TrCH #1 ) or a second transportchannel (TrCH #2). Each of the transport channels is supported by adifferent physical resource and the selected transport channel ismultiplexed with other transport channels before being transmitted onthe physical resource. The selection of the specific transport channelfor the scheduling assistance data may be made in response tocharacteristics of the physical resources associated with the individualtransport channels.

In some embodiments the transport channels of the physical resource maybe terminated at different points in the fixed network. Specifically, atransport channel may be used for user data communication and may beterminated at the RNC 107 while a second transport channel is used forcommunication of the scheduling assistance data and is terminated in thebase station 105. Thus, the same physical resource may support transportchannels which are individually terminated at the optimum location. Thismay reduce delays associated with the scheduling assistance data and mayimprove the scheduling performance of the base station scheduler 209.

FIG. 4 illustrates an example of a signaling system in accordance withsome embodiments of the invention. The illustrated functionality mayspecifically be implemented in the channel controller 213 of FIG. 2. Theoperation will be described with reference to the three specificexemplary 3GPP UTRAN TDD scenarios previously described.

Scenario 1

In scenario 1, due to the fact that the existing RACH is terminated inthe RNC 107, the base station 105 cannot make use of this transportchannel to carry the necessary uplink signaling. The RACH is not“visible” to the base station 105 and simply passes through it on itsway to the RNC. It would be possible to forward the received informationback from the RNC to the Node-B via new lub signaling although thistechnique suffers greatly from the latency involved in these multipletransmission legs.

Non-random-access methods may also be considered (such as circularpolling) but such techniques again suffer from potential latencyincreases (there is a potential significant delay between data arrivingin the user's transmission buffer(s) and uplink resources being grantedto serve that data).

In accordance with the example of FIG. 4, a new base station terminatedrandom access channel which is able to convey the scheduling assistancedata directly to the base station scheduler 209 is defined.

The new random access channel is termed “E-SACH_(R)” (Enhanced UplinkScheduler Assistance Channel) in the example of FIG. 4. The “R”subscript relates to the fact that the channel is random access innature (ie: non-scheduled and in particular not scheduled or managed bythe base station scheduler 209). The channel is able to carry anindication to the base station scheduler 209 that new data has arrivedin the user's transmission buffer and is in effect a request for uplinkradio resources. It may also carry an indication of the current channelconditions and, because the transmission is random access, it may alsocarry an indication of the user identity such that the base stationscheduler 209 knows which user to allocate the resources to.

Scenario 2

With the uplink data payload being carried on one transport channelscheduled by the base station scheduler 209 (denoted theEnhanced-Dedicated CHannel—E-DCH), the uplink signaling may be carriedon a separate transport channel (denoted E-SACH_(E) in FIG. 4). LikeE-SACH_(R), E-SACH_(E) is terminated at the base station 105. The “E”subscript is used to denote that the scheduling assistance informationis piggy-backed on the enhanced uplink transmission scheduled by thebase station scheduler 209. However, because it is conveyed on ascheduled transmission, the need to carry the user identity in thesignaling is obviated. Thus, the PDU size of an E-SACH_(E) PDU is likelyto be different to that of an E-SACH_(R) PDU. The two (or more)transport channels are multiplexed onto the same set of physicalresources (termed a CCTrCH). Furthermore, it is possible to adjust thedegree of FEC coding applied to E-SACH_(E) and E-DCH, to optimize thetransmission reliability of each transport channel as desired. Forexample, it may be desirable for the E-SACH_(E) to be given a higherdegree of FEC protection than the E-DCH, such that the schedulerinformation gets to the scheduler with high reliability (usually in asingle transmission) whilst the E-DCH is able to utilize the ARQ(retransmission) efficiencies by operating each transmission instance atoptimum link reliability (often involving multiple transmissions perunit of data before it is received without error).

Scenario 3

This scenario is similar to that of scenario 2, with the key differencebeing that the uplink signaling is piggybacked on uplink resources whichare not directly associated with the enhanced uplink transmission andwhich are not scheduled by the base station scheduler 209. These uplinkresources are here termed “auxiliary”. For example, enhanced packet datauplink may be used in conjunction with the HSDPA downlink packet dataservice. In such a case an associated uplink DCH exists (typically usedto carry higher layer user data such as TCP (Transmit Power Control)acknowledgements, and layer 3 control traffic to control events (such ashandovers). The scheduling assistance data may in such a case betransmitted on uplink DPCH physical resources or on another uplink HSDPAchannel such as the HS-SICH (High Speed-Shared Information Channel).

When no other uplink transmission resources are available, but there isa need to send updated information to the scheduler, it may bepreferable (for latency reasons or to reap efficiency savings) for theuser to piggyback the uplink signaling of scheduling assistance dataonto the auxiliary uplink resources, rather than using the E-SACH_(R)random access procedures.

Again, in order to facilitate control over the degree of forward errorcorrecting coding applied to the auxiliary traffic and the uplinksignaling, and to enable separate detection of each, a separatetransport channel is used for the uplink signaling, termed theE-SACH_(D). As in scenario 2, the E-SACH_(D) is terminated at basestation 105 and is multiplexed together with other data onto a commonset of auxiliary uplink radio resources (the auxiliary uplink CCTrCH).

It will be appreciated that the above description for clarity hasdescribed embodiments of the invention with reference to differentfunctional units and processors. However, it will be apparent that anysuitable distribution of functionality between different functionalunits or processors may be used without detracting from the invention.For example, functionality illustrated to be performed by separateprocessors or controllers may be performed by the same processor orcontrollers. Hence, references to specific functional units are only tobe seen as references to suitable means for providing the describedfunctionality rather than indicative of a strict logical or physicalstructure or organization.

The invention can be implemented in any suitable form includinghardware, software, firmware or any combination of these. The inventionmay optionally be implemented at least partly as computer softwarerunning on one or more data processors and/or digital signal processors.The elements and components of an embodiment of the invention may bephysically, functionally and logically implemented in any suitable way.Indeed the functionality may be implemented in a single unit, in aplurality of units or as part of other functional units. As such, theinvention may be implemented in a single unit or may be physically andfunctionally distributed between different units and processors.

Although the present invention has been described in connection withsome embodiments, it is not intended to be limited to the specific formset forth herein. Rather, the scope of the present invention is limitedonly by the accompanying claims. Additionally, although a feature mayappear to be described in connection with particular embodiments, oneskilled in the art would recognize that various features of thedescribed embodiments may be combined in accordance with the invention.In the claims, the term comprising does not exclude the presence ofother elements or steps.

Furthermore, although individually listed, a plurality of means,elements or method steps may be implemented by e.g. a single unit orprocessor. Additionally, although individual features may be included indifferent claims, these may possibly be advantageously combined, and theinclusion in different claims does not imply that a combination offeatures is not feasible and/or advantageous. Also the inclusion of afeature in one category of claims does not imply a limitation to thiscategory but rather indicates that the feature is equally applicable toother claim categories as appropriate. Furthermore, the order offeatures in the claims do not imply any specific order in which thefeatures must be worked and in particular the order of individual stepsin a method claim does not imply that the steps must be performed inthis order. Rather, the steps may be performed in any suitable order. Inaddition, singular references do not exclude a plurality. Thusreferences to “a”, “an”, “first”, “second” etc do not preclude aplurality.

1. An apparatus for transmitting signaling information in a cellularcommunication system; the apparatus comprising: means for generatingscheduling assistance data for a base station based scheduler, thescheduling assistance data relating to packet data communication of aUser Equipment; means for allocating the scheduling assistance data to afirst transport channel; means for allocating other data to a secondtransport channel; means for transmitting the first and second transportchannel as multiplexed transport channels on a first physical resource;wherein the second transport channel employs a retransmission scheme andthe first transport channel does not employ a retransmission scheme. 2.The apparatus claimed in claim 1 wherein the means for transmitting isarranged to transmit the first and second transport channels withdifferent transmission reliabilities.
 3. The apparatus claimed in claim2 wherein the means for transmitting is arranged to transmit the firsttransport channel with a lower bit error rate than for the secondtransport channel.
 4. The apparatus claimed in claim 1 wherein the meansfor transmitting is arranged to transmit the first transport channel inaccordance with a first transmission scheme and to transmit the secondtransport channel in accordance with a different second transmissionscheme.
 5. The apparatus claimed in claim 4 wherein the firsttransmission scheme and the second transmission scheme comprisedifferent error correcting encoding.
 6. The apparatus claimed in claim 1wherein the means for transmitting is arranged to perform rate matchingof the first transport channel and the second transport channel.
 7. Theapparatus claimed in claim 6 wherein the means for transmitting isarranged to apply different rate matching characteristics to the firsttransport channel and the second transport channel.
 8. The apparatusclaimed in claim 1 wherein the first transport channel is terminated ina base station of the base station based scheduler.
 9. The apparatusclaimed in claim 1 wherein the first transport channel has a differenttermination point than the second transport channel.
 10. The apparatusclaimed in claim 1 wherein the retransmission scheme is a Radio NetworkController controlled retransmission scheme.
 11. The apparatus claimedin claim 1 wherein the retransmission scheme is a Base Stationcontrolled retransmission scheme.
 12. The apparatus claimed in claim 1wherein the retransmission scheme is a Hybrid Automatic Repeat reQuest,ARQ, retransmission scheme.
 13. The apparatus claimed in claim 1 furthercomprising means for transmitting the scheduling assistance data using asecond physical resource and selection means for selecting between thefirst physical resource and the second physical resource.
 14. Theapparatus claimed in claim 13 wherein the selection means is arranged toselect between the first physical resource and the second physicalresource in response to an availability of the first physical resourceand the second physical resource
 15. The apparatus claimed in claim 13wherein the selection means is arranged to select between the firstphysical resource and the second physical resource in response to atraffic loading of the first physical resource and the second physicalresource.
 16. The apparatus claimed in claim 13 wherein the firstphysical resource is not managed by the base station based scheduler.17. The apparatus claimed in any of the claims 13 to 16 wherein thesecond physical resource is a physical resource managed by the basestation based scheduler.
 18. The apparatus claimed in claim 13 whereinthe first physical resource is associated with the first transportchannel and the second physical resource is associated with a thirdtransport channel and the selection means is arranged to allocate thescheduling assistance data by associating the scheduling assistance datawith the first or third transport channel.
 19. The apparatus claimed inclaim 1 wherein the first physical resource is a random access channel20. The apparatus claimed in claim 1 wherein the packet datacommunication is an uplink packet data communication.
 21. The apparatusclaimed in claim 1 wherein the cellular communication system is a 3^(rd)Generation Partnership Project, 3GPP, system.
 22. The apparatus claimedin claim 1 wherein the cellular communication system is a Time DivisionDuplex system.
 23. An apparatus for receiving signaling information in acellular communication system; the apparatus comprising: means forreceiving a first physical resource comprising a first transport channeland a second transport channel as multiplexed transport channels; meansfor extracting scheduling assistance data for a base station basedscheduler from the first transport channel, the scheduling assistancedata relating to packet data communication of a User Equipment; meansfor extracting other data from the second transport channel; and whereinthe second transport channel employs a retransmission scheme and thefirst transport channel does not employ a retransmission scheme.
 24. Amethod of transmitting signaling information in a cellular communicationsystem; the method comprising: generating scheduling assistance data fora base station based scheduler, the scheduling assistance data relatingto packet data communication of a User Equipment; allocating thescheduling assistance data to a first transport channel; allocatingother data to a second transport channel; transmitting the firsttransport channel and second transport channel as multiplexed transportchannels on a first physical resource; and wherein the second transportchannel employs a retransmission scheme and the first transport channeldoes not employ a retransmission scheme.
 25. The method claimed in claim24 wherein the first transport channel and the second transport channelare transmitted with different transmission reliabilities.
 26. Themethod claimed in claim 24 wherein the first transport channel istransmitted in accordance with a first transmission scheme and thesecond transport channel is transmitted in accordance with a differentsecond transmission scheme.
 27. The method claimed in claim 24 whereinthe first transport channel is terminated in a base station of the basestation based scheduler.
 28. A method of receiving signaling informationin a cellular communication system; the method comprising: receiving afirst physical resource comprising a first transport channel and asecond transport channel as multiplexed transport channels; extractingscheduling assistance data for a base station based scheduler from thefirst transport channel, the scheduling assistance data relating topacket data communication of a User Equipment; extracting other datafrom the second transport channel; and wherein the second transportchannel employs a retransmission scheme and the first transport channeldoes not employ a retransmission scheme.